The present invention relates generally to machines and tools for cutting and shaping wood. More particularly, the present invention relates to hold down and guarding devices for use in conjunction with machines and tools for cutting and shaping wood.
Many woodworking methods such as routing, joining and cutting involve the step of moving a workpiece past a rotating cutting tool. These operations are typically performed on a woodworking machine having a worktable. Examples of such machines include router tables, shapers, joiners, jointers, and table saws. Examples of rotating cutting tools include saw blades and router bits. When performing a woodworking operation on a table such as routing, joining and cutting the machine operator must control the path of the workpiece as it moves relative to the cutting tool. The motion of the workpiece is typically guided in whole or in part by hand.
Various safety devices may be utilized to minimize the inherent dangers of woodworking. For example, a safety device may seek to reduce the likelihood that a woodworkers hand will contact the cutting tool. By way of a second example, a safety device may seek to reduce the likelihood that a workpiece will thrown at the woodworker. One example of a situation in which a workpiece is thrown at a woodworker is an occurrence known in the art as kickback.
One type of kickback occurs when the workpiece binds to a cutting tool, for example the blade of a table saw. As a workpiece is cut on a table saw, the blade removes material from the workpiece creating an elongate kerf through the workpiece. Residual stresses within the workpiece sometimes cause the material of the workpiece to close around the blade. A portion of the workpiece may bind to the blade, causing the workpiece to be carried along with the blade as it rotates at high speed. When kickback occurs, the workpiece may be thrown upwardly and rearwardly toward the body of the saw operator. The workpiece may strike the unfortunate operator causing bodily injury.
One example of a safety device that is used frequently by woodworkers is a feather board. A feather board typically includes a plurality of fingers or pawls. The pawls are typically biased so that they ride over a surface of the workpiece as it is fed in a forward direction past the cutting tool. When a kickback situation arises while a feather board is being used, the workpiece begins movement in a reverse direction causing a corresponding rotation of the pawls. As the pawls rotate, they may jam the workpiece against a fence mounted on the table of the machine, thereby preventing any further reverse movement. In addition, when a raised panel is formed on a router, for example, the router may undercut the wood beneath the feather board. The feather board can then apply downward force on the wood which is unsupported below the feather board. This can result in the workpiece tipping out of plane toward the feather board.
The present invention relates generally to machines and tools for cutting and shaping wood, which overcomes many of the limitations of the prior art. More particularly, the present invention relates to hold down and guarding devices for use in conjunction with machines and tools for cutting and shaping wood. A guard for use with a woodworking machine having a worktable and a cutting tool for performing operations on a workpiece is disclosed. A guard in accordance with the present invention features a guard member having a body portion, a workpiece engaging portion, and a machine engaging portion. The workpiece engaging portion of the guard member includes a workpiece engaging surface. The workpiece engaging surface is preferably configured such that the body portion of the guard member is deflected when the workpiece is urged against the workpiece engaging surface in a direction substantially parallel to a working surface of the worktable for engagement with the cutting tool.
In certain implementations of the invention, the workpiece engaging surface of the workpiece engaging portion of the guard member features a rounded surface defining a tangent line disposed at an angle relative to the working surface of the worktable. In an advantageous embodiment, the angle between the tangent line and the working surface is an acute angle.
In other implementations of the invention, the workpiece engaging surface of the workpiece engaging portion of the guard member features a surface defining a plane disposed at an angle relative to the working surface of the worktable. In an advantageous embodiment, the angle between the plane and the working surface is an acute angle.
In an advantageous embodiment of the present invention, the workpiece engaging portion of the guard member comprises a low friction material. In a particularly advantageous embodiment of the present invention, the workpiece engaging portion of the guard member comprises ultra high molecular weight polyethylene.
In one aspect of the present invention, the body portion of the guard member is configured such that the workpiece engaging portion of the guard member exerts a force on the workpiece in the direction of the worktable when the body portion of the guard member is deflected.
In an advantageous embodiment of the present, the body portion of the guard member comprises an arcuate wall. In a particularly advantageous embodiment the body portion of the guard member comprises an arcuate wall having an undeflected shape having a first radius, and a deflected shape having a second radius, wherein the second radius is generally greater than the first radius.
In an advantageous embodiment of the present invention, the body portion of the guard member comprises a resilient material. Examples of resilient materials that may be suitable in some applications include polycarbonate and acrylic.
In an additional aspect of the present invention, the body portion of the guard member may comprise a substantially optically transparent material. Examples of optically transparent materials that may be suitable in some applications include polycarbonate and acrylic.
In yet another aspect of the present invention, the machine engaging portion of the guard member includes means for releasably fixing the guard member to the wood working machine. In certain implementations of the invention, the machine engaging portion of the guard member includes means for releasably fixing the guard member to a fence of the wood working machine. For example, the machine engaging portion of the guard member defines a plurality of slots.